- Turn the filter counter-clockwise to loosen it.
- Remove the filter from the probe. Be careful not to touch the sensors with the filter. Without the filter in place, the sensors are easily damaged – handle the probe carefully.
- Check that the O-ring is undamaged and in place.
- Install a new filter on the probe, and tighten it so it is finger-tight. Make sure the filter sits straight and meets the threads properly.
New filters can be ordered from Vaisala. For available filters, see Filter Types. For order codes of the filters, see Accessories.